<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<script>
			var score = prompt('请输入成绩');
			if (score >= 90) {
				alert('A');
			} else if (score >= 80) {
				alert('B')
			} else if (score >= 70) {
				alert('C')
			} else if (score >= 60) {
				alert('D')
			}
		</script>
	</head>
	<body>
	</body>
</html>
